Lightweight panels having cellular plastics cores sandwiched between durable outer skins of sheet plastics, metal, timber, cementitious materials, and the like have found favour as thermal insulation members in cold rooms, cold storage warehouses and building structures located in adverse climates. Typically such insulating panels comprise a core of open or closed cell polystyrene or polyurethane foam.
WO 89/00496 filed by the applicant provides a process and apparatus for producing laminated panels. Whilst this process and apparatus are effective in producing high quality foamed plastic laminated panels for modular building structures, it does not provide for high volume production due, in part, to the inability to readily alter the size of the panels. The presses of WO 89/00496 had large heavy steel planar platens to withstand the internal pressures. These steel platens required that the panels be held in the press for longer periods, as the decreased temperature of the platens acted as a heat sink, which along with the substantial cooling effect of the adiabatic expansion of the blowing agent, slowed the cross-linking reaction, and thus extending the mould cycle. The steel platen surfaces also required preheating in cold weather in order to minimise their interference with the cross-linking reaction.
Attempts to speed up the process of WO 89/00496 resulted in panels having uneven insulation properties, due to variations in foam density as a function of ambient temperature. The areas of the panels with less insulation may lead to the formation of condensation. It is therefore important to have close control of reaction rates, otherwise variable quality of the panel results, which is unacceptable in building materials.
The arrangement of the injection mould presses in WO 89/00496 required that the second outer skin layer be placed on the movable steel platen surface and under actuation of the clamp join with the seals to form a mould cavity. The technique of adding the second skin layer limited the length of the moulds to 15 m of less.
The regulated phasing out of the use of reactants, such as Freon 11 (the blowing agent used in the production of polyurethane), has required a move to more environmentally acceptable halogenated hydrocarbons.
These halogenated hydrocarbons require additional clamping pressures to be used to ensure the press remains closed during the expansion of the blowing agent in the cross-linking reaction.